Apparatus for assembling battery plates

ABSTRACT

This invention relates to apparatus for assembling battery plates and includes mould, generally indicated at 10 which defines a pair of ducts 11, 12 which supply respective sets of mould cavities 13, 14 via weirs 15. Each feed duct 11,12 has a respective pair of feed passages 16, 17 and 18, 19 extending beneath it and is interconnected to the respective feed passages by generally vertical passages 20, 21. The feed passages 16-18 are fed by a pump.

This invention relates to an apparatus for assembling battery plates.

The term "battery" is used herein to include accumulators. In aconventional lead-acid battery it is customary to connect together theplates of each stack by means of a lead strap or post which is fixed toaligned lugs or tabs on the plates. Apparatus for casting such straps orpost onto plate lugs is described in our British Patent No. 2023471B. Inthis apparatus there is a mould having at least one battery strap orpost mould cavity and a molten feed duct adjacent thereto, a weirbetween the feed duct and the cavity and a lead supply passage below theduct and connected to the duct by vertical passages through which leadcan well up into the duct when lead is pumped into the passage, and thespill over the weir into the cavity. A suitable pumping arrangement isdescribed in International Patent Application No. WO 91/05625.

It is now desired to use bigger moulds, for example a single mould forassembling the plates of two batteries disposed end to end with oneanother or for large configuration batteries, such as truck batteries.It will be understood that this requires twice as much lead to bedelivered to the mould in a comparable time scale. The obvious solutionsare either to increase the flow rate through the lead supply passage orto double the cross-sectional area of the passage. The first leads tounderfilling of the upstream end of the duct and overfilling of thedownstream end of the duct as soon as the lead supply is shut off,whilst the latter results in geyser-like jets shooting up the upstreamvertical passages.

One aspect of the invention provides an apparatus for connecting abattery plate to a metal strap or post, including a mould having a setof post or strap mould cavities, a molten metal feed duct adjacentthereto, a weir between the feed duct and the cavities, means forsupplying molten lead to the duct, and hence the cavities, including apump and at least a pair of feed passages extending below the duct andconnected to the duct.

The provision of at least two feed passages has surprising advantages.First they are able to supply a large quantity of lead at a relativelylow velocity, thus avoiding problems arising from the lead having excesskinetic energy, such as the unequal lead levels in the duct and secondlythe mass of lead in each feed passage at the beginning of an operationalcycle is relatively low and so the lead can be smoothly acceleratedwithout creating the geyser effect mentioned above.

In one preferred arrangement one feed passage is connected to the ductalong or for substantially over half of the length of the duct, whilstthe other feed passage is connected to the duct along or forsubstantially the other half of the duct. If the connection between thehalf of the duct, which in flow terms, is nearest the pump, is displacedfurther from its associated cavities than the connection for the half ofthe duct which is furthest, in flow terms, from the pump, then the rateof emptying of the duct can to at least some extent be balanced.

Preferably the pump is a variable speed pump and conveniently theapparatus further comprises means for increasing the speed of the pumpas metal is supplied to the duct and for subsequently reducing the speedof the pump. The pump may be a continuous rotary pump and may forexample be of the type described in International Patent Application No.WO 91/05625.

The feed passages are preferably parallel and connected to the duct bygenerally vertical passages up which the lead can well.

In at least one embodiment there are two parallel sets of mouldcavities, each having a molten feed duct and at least a pair of feedpassages extending below each of the ducts and connected to theirrespective duct.

In that case the apparatus may further include at least one displacementbody insertable into the mould to vary the volume of a duct and itsassociated cavities, so that it can be balanced with the volume of theother duct and cavities.

In any of the above arrangements the or each set of mould cavities mayinclude cavities for more than one battery, in which case the cavitiesof the respective batteries are conveniently arranged in line, one withthe other.

Although the invention has been defined above it is to be understoodthat it includes any inventive combination of the features set out aboveor in the following description.

The invention may be performed in various ways and a specific embodimentwill now be described with reference to the accompanying drawings, inwhich:

FIG. 1 is a view from above of a mould for use in assembling batteryplates;

FIG. 2 is an end view on arrow A;

FIG. 3 is a cross-sectional view on the line III to III in FIG. 1; and,

FIG. 4 is a longitudinal section of the mould of FIG. 1 taken along theline IV to IV.

A mould is generally indicated at 10 and defines a pair of feed ducts11, 12 which supply respective sets of mould cavities 13, 14 via weirs,some of which are indicated at 15. The basic construction and operationof these features is identical to that described in our British PatentNo. 2023471B and the description of that Patent is incorporated intothis specification for these purposes. The mould 10 is however twice thelength of the mould described in our earlier Patent so that it providesmould cavities 13, 14 for two batteries, the respective groups ofcavities being on either side of the line B.

Each feed duct 11, 12 has a respective pair of feed passages 16, 17 and18, 19 extending beneath it and to either side and is interconnected toits respective feed passages by generally vertical passages 20, 21. Thefeed passages are in turn connected to a T-connector 22 having aninlet/outlet 23 which is connected to a lead pot and pump assembly ofthe type described in International Patent Application No. WO 91/05625.

It will be noted that the feed ducts 11, 12 and the feed passages 16-19are formed in separate elements of the mould from the cavities 13, 14.This is to enable the central portion 24 to be cooled on casting, whilstthe wing portions 25, 26 are maintained heated.

As has previously been mentioned the mould 10 operates basically in themanner described in the above mentioned Patent and Application. It ishowever distinguished from these, in as much as it is designed to mouldtwice as many posts and straps within an appropriate cycle time. Thismeans that twice as much lead has to be delivered from the lead pot (notshown) into the feed ducts 11, 12 within an acceptable time. The obviousways of attempting to achieve that would have been to use the existingsupply arrangement and simply drive the pump twice as fast or to doublethe cross-sectional area of the feed passage or a compromise combinationof the two. Surprisingly these approaches are not appropriate, becausethe first introduces far too much energy into the lead within the feedpassage and it is extremely difficult to control the lead, particularlywhen it is to be sucked back. Alternatively if the cross-sectional areais doubled then the velocity of the lead is to some extent decreased butthe energy still remains relatively high. This might be overcome byfurther increasing the cross-sectional area of the feed passage, but inpractice such an approach proves to be impractical, because the mass oflead in the feed passage at start up is so great that either a very highlocal pressure is created, due to the lead's inertia, at the upstreamend of the feed passage causing geysers of lead to shoot up the upstreamvertical passages 20, 21 or if the lead is accelerated slowly the timetaken to fill the mould cavities exceeds the acceptable cycle time ofthe apparatus.

In fact these problems can be overcome by the provision of more than onefeed passage for each duct. This enables the feed passages to have atotal cross-sectional area which is high enough to reduce the feedvelocity, and hence the energy, to acceptable levels, but at the sametime prevents the mass of lead in any particular feed passage reaching alevel where it is difficult to slowly and smoothly accelerate the leadwithin an acceptable time. Thus despite the fact that frictional andconstructional considerations would lead one away from introducingmultiple feed passages, this is in fact the appropriate solution.

It will be appreciated that to achieve the desired smooth accelerationof the lead a rotary pump of the type described in International PatentApplication No. WO 91/05625 is extremely desirable but any appropriatelead supply stream can be used. Depending on the dimensions and demandsof the mould, it may be appropriate to use more than two feed passagesfor each duct and they could be fed directly and individually from thelead pot.

It is desirable that the volume created by a feed duct and itsassociated cavities is equal to the equivalent volume of the other feedduct and its cavities. If it is not, then cavity volume filling willtake place at different rates with the result that the filling part ofthe cycle will take too long. In order to allow for such a balancingoperation to take place, removable displacement bodies 27 are provided.By selecting bodies of different sizes, the volume can be fine tuned.

It will also be noted that the bottom of each feed duct 11, 12 as itapproaches the weir 15 is formed as a ramp beach-like portion 28 toassist in the dissipation of any waves which may be set up within thefeed ducts 11, 12. However in at least some configurations this may leadto such a slow rise in the lead level in the duct that an even breakover the weirs 15 may not be achieved. In that case the ramp 28 may bereplaced by a narrow channel to provide a more rapid rise.

When the lead is allowed to drain back down out of the ducts 11, 12,there may be significant time lag between when the lead starts to drainfrom the end of the ducts to the left of the line B in FIG. 1 and whenthe lead starts to drain from the ends of the ducts to the right of lineB. This means that the `left` end can fall to a lower level than isnecessary and hence more lead needs to be pumped back in for the nextmould. Cycle time is hence increased. This can to some extent beovercome by blocking at least some of the vertical channels 21 to theleft of line B, as shown in FIG. 3 at 21a, and at least some of thevertical channels 20 to the right of line B. This has the effect ofrelatively increasing the path that the lead to the left of line B hasto travel and also makes it easier to start lead flowing at the righthand end of duct 19.

I claim:
 1. Apparatus for connecting a battery plate to a metal strap orpost, including a mould having a set of post or strap mould cavities, amolten metal feed duct adjacent thereto, a weir between the feed ductand the cavities, means for supplying molten lead to the duct, and hencethe cavities, including a pump and at least a pair of feed passagesextending below the duct and connected to the duct.
 2. Apparatus asclaimed in claim 1 wherein one feed passage is connected to the ductalong substantially one half of the length of the duct, whilst the otherfeed passage is connected to the duct along substantially the other halfof the duct.
 3. Apparatus as claimed in claim 2 wherein the connectionbetween the half of the duct which is nearest the pump, is displacedfurther from its associated cavities than the connection for the half ofthe duct which is furthest from the pump.
 4. Apparatus as claimed inclaim 1 wherein the feed passages are substantially parallel andconnected to the duct by generally vertical passages up which lead canwell.
 5. Apparatus as claimed in claim 1 wherein the pump is a variablespeed pump.
 6. Apparatus as claimed in claim 4 further comprising meansfor increasing the speed of the pump as metal is supplied to the ductand for subsequently reducing the speed of the pump.
 7. Apparatus asclaimed in claim 1 further comprising two parallel sets of mouldcavities, each having a molten feed duct and at least a pair of feedpassages extending below each of the ducts and connected to theirrespective duct.
 8. Apparatus as claimed in claim 7 wherein theapparatus further includes at least one displacement body insertableinto the mould to vary the volume of a duct and its associated cavities,so that it can be balanced with volume of the other duct and cavities.9. Apparatus as claimed in claim 7 wherein said set of mould cavitiesincludes cavities for more than one battery.